English verb conjugation
CAN MODIFY

Regular verb: modify - modified - modified

Affirmation

Simple form	V-ing form
I can modify you can modify he can modify we can modify you can modify they can modify	I can be modifying you can be modifying he can be modifying we can be modifying you can be modifying they can be modifying
Perfect	V-ing perfect
I can have modified you can have modified he can have modified we can have modified you can have modified they can have modified	I can have been modifying you can have been modifying he can have been modifying we can have been modifying you can have been modifying they can have been modifying

Negation

Simple form	V-ing form
I can't modify you can't modify he can't modify we can't modify you can't modify they can't modify	I can't be modifying you can't be modifying he can't be modifying we can't be modifying you can't be modifying they can't be modifying
Perfect	V-ing perfect
I can't have modified you can't have modified he can't have modified we can't have modified you can't have modified they can't have modified	I can't have been modifying you can't have been modifying he can't have been modifying we can't have been modifying you can't have been modifying they can't have been modifying

Interrogative form

Simple form	V-ing form
can I modify? can you modify? can he modify? can we modify? can you modify? can they modify?	can I be modifying? can you be modifying? can he be modifying? can we be modifying? can you be modifying? can they be modifying?
Perfect	V-ing perfect
can I have modified? can you have modified? can he have modified? can we have modified? can you have modified? can they have modified?	can I have been modifying? can you have been modifying? can he have been modifying? can we have been modifying? can you have been modifying? can they have been modifying?

Interro-negative form

Simple form	V-ing form
can't I modify? can't you modify? can't he modify? can't we modify? can't you modify? can't they modify?	can't I be modifying? can't you be modifying? can't he be modifying? can't we be modifying? can't you be modifying? can't they be modifying?
Perfect	V-ing perfect
can't I have modified? can't you have modified? can't he have modified? can't we have modified? can't you have modified? can't they have modified?	can't I have been modifying? can't you have been modifying? can't he have been modifying? can't we have been modifying? can't you have been modifying? can't they have been modifying?